Apparatus for continuous metal production and continuous gas plating



Apnl 10, 1956 H. A. TOULMIN, JR 2,741,216

APPARATUS FOR CONTINUOUS METAL PRODUCTION AND CONTINUOUS GAS PLATING Original Filed Sept. 10, 1949 INVENTOR ,Zn 4. 7071/hn'n Jr.

A TTO RNEYS APPARATUS FOR CONTINUOUS METAL PRODUC- TION AND CONTINUOUS GAS PLATING Harry A. Toulmin, 3n, Dayton, Ohio, assignor to The Commonwealth Engineering Company of Ohio, Dayton, Ohio, a corporation of Ohio Original application September 19, 1949, Serial No. 115,033, now Patent No. 2,657,457, dated November 3, 1953. Divided and this application February 11, 1952, Serial N 0. 27 0,920

4 Claims. (Cl. 118-48) This invention relates to protective metal coatings.

More particularly, it relates to the coating of cast metals by deposition of protective metals through decomposition of volatile metal compounds, and apparatus for carrying out the process.

This application is a division of my copending application, Serial No. 115,033, filed September 10, 1949, now Patent No. 2,657,457.

Special types of carbon and alloy steel and nonferrous alloys have been manufactured heretofore by pouring the molten metal into ingot molds.

Large size ingots while still hot are removed from the molds and shipped to the soalc'ng pits where they are held until the internal and external ingot temperatures equalize.

The soaked ingots then are rolled in blooming mills into billets preparatory to further processing.

Rough billets require more or less surface conditioning because, for example, the steel is particularly prone to form loose scale and become badly oxidized while cooling, thus necessitating the surface treatment.

This process has now been at least partially superseded It is an object of the present invention to overcome the limitations and disadvantages of the process known heretofore.

It is also an object of the present invention to prepare cast metal objects having a protective coating of a non-oxidizing metal.

It is another object of this invention to prepare cast steel of reduced scaling character.

It is still a further object of this invention to prepare cast steel with ductile protective metal coatings which do not interfere with further processing such as rolling. It is still another object of this invention to prepare cast metals having protective coatings not depositable by electrolytic methods.

In brief, the process is carried out by casting metals and when the continuous ribbon on hot but solidified metal issues from the mold, bringing the hot metal into contact with vapors of decomposable metal compounds.

'In this way at least a portion of the heat in the molded material instead of being wasted is utilized to decompose volatile metal compounds and deposit a protective coat In sequence the molten metal is poured into a shaping mold and cooled to a solid form. The formed cast metal progresses through an insulating sleeve, where cooling is controlled until the cast metal is reduced to 600 F., depending upon the type of metal being cast and the thickness of the casting.

This hot metal then progresses through a plating chamber where the temperature of the metal decomposes vapors of volatile metal compounds continuously fed into contact with the continuously moving cast object.

The metal at this stage is solidified to the point where its speed of movement may be controlled by a roll drive or equivalent mechanism.

The plated cast metal is then cut to desired length by suitable means such as saws, acetylene torches, and the like.

In the plating step the hot cast metal is brought into contact with continuously changing atmosphere which is made up of gaseous material, at least a portion of which is decomposable at the temperature of the continuously moving cast metal to deposit a metal coating.

Inasmuch as the cast metal is progressing continuously through this chamber, one of the factors important to the successful operation is control of gas pressure not only within the plating chamber itself, but in each of the surrounding annular spaces, of design which will hereafter be explained.

In order to insure against leakage of plating gases which are toxic from the plating chamber and still have openings in the partition walls for the continuous passage of the cast metal, it is necessary to maintain a metalvapor free gas atmosphere at a slightly higher gas pressure in the annular spaces surrounding the plating chamber.

The leakage of inert gas into a plating chamber is limited to small quantities by having apertures in the partition walls of a configuration providing a loose sliding fit with the object passing therethrough or enlarged holes with shims encircling the moving object in close proximity to these holes and by keeping the pressure differential small.

It will be recognized that the inert gas leaking into the plating chamber is not a harmful operation because the metal-bearing gases are usually diluted with an inert gaseous medium and the gas decomposing reaction in the plating chamber produces relatively inert decomposition products.

The stream of gaseous material brought into contact with the hot cast metal may be formed by mixing an inert gas with the vapors of a volatile metal compound or by atomizing .a liquid metal compound into a blast of hot inert gas or other equivalent method.

Carbon dioxide, helium, nitrogen, hydrogen, the gaseous product of controlled burning of hydrocarbon gases free of oxygen, and the like, have been utilized as a carrier medium or inert gas medium.

I ample, petroleum ether), also nitroxyl compounds, nitrosyl carbonyls, metal hydrides, metal alkyls, metal a temperature in the range of approximately 300 to halides, and the like. I

Illustrative compounds of the carbonyl type are nickel, iron, chromium, molybdenum, cobalt, and mixed car- 4 bonyls.

- Illustrative compounds of other groups are the nitroxyls, such as copper nitroxyl; nitrosyl carbonyls, for example, cobalt nitrosyl carbonyl; hydrides, such as antimony hydride,- tin hydride; metal alkyis, such as chromyl chloride; and carbonyls halogens, for example, osmiumcarbonyl bromide, ruthenium carbonyl chloride, and the like.

Each material from which a metal may be plated has a temperature at which decomposition is complete. How ever, decomposition may take place slowly at a lower temperature or while the vapors are being raised in temperature through some particular range, For example,

nickel carbonyl completely decomposes at a temperature ing with most metal carbonyls we prefer to operate in a temperature range of 375 F. to 425 I The process is illustrated without provision for annealing the deposited coating in order to increase their adhesion and ductility. If such an operation is desired provision can be made for an anneal in the inert gas filled annular space, as will be more definitely explained.

Annealing temperatures are higher than plating temperatures and generally in the range of 800 to 1200 F. An anneal may be carried out; for'example, by induction heating. 7

The invention will be more clearly understood from the following description taken in connection with the drawing which: i

Figure 1 is a diagrammatic elevational view of a complete unit for continuously casting and plating metals; and

Figure 2. is an enlarged sectional view equipment.

'Referring to the drawings, there is illustrateda continuous method of casting and plating as utilized in connection with steel manufacture without any intention that the invention be limited thereto.

In Figure 1 there is shown the supporting framework 10 of a multi-story building. On the top fioor of said building framework 10 supports tracks 11 for a movable overhead'crane 12. I

A ladle 13 is'suspended from crane 12 by suitable cables 14. Ladle 13 is shown suspended over a heated holding ladle 15. Ladle 15 is actuated fortip ping and pouringby suitable means 16 such as pulleys or levers.

Adjacent the ladle 15 is a liquid-cooled mold 17 in which ladle 15 is adapted to empty. A cast steel tube 18 is shown issuing from the mold 17 and moving downward through an insulating sleeve 19 within which there is generally maintained an atmosphere of hydrogen.

Steel tube 18 moves downward from the sleeve 19 through a unit 20 designed to accurately maintain and control the temperature of the steel tube. Steel tube 18 passes on downwardthrough a plating unit 21 which will be described in more detail.

Plated steel tube is drawn downward at a predetermined rate, generally in the range of 3 to 7 feet per minute for a tube of about 3 inch radius, by squeeze rolls 22.

The coated steel tube is cut into predetermined lengths of the plating -by an acetylene torch 23 and the tubular units lowered to the horizontal by suitable cradle means 24.

Referring to Figure 2, it will be seen that the plating unit 21 consists of an inner wall member 30 and outer wall members 31 and 32, which enclose annular spaces or chambers 33 and 34, respectively. I 7

Each of the wall members is providedwith two aligned ports indicated as a and b, respectively, of size adapted for close sliding fit with the steel tube 18 passing vertically downward therethrough. The closure of each chamber may be tightened by use of shims indicated as cand d.

The inner chamber is provided with gas inlet and outlet means 35 and 36, respectively. Chamber. 33 is provided with gas inlet and outlet means 37 and' 38, respec-' tively. Chamber. 34 is provided with inlet and outlet means 39 and 40, respectively. Outlet means 40 is adapted with an exhaust means 41, such as a fan, for maintaining less than atmospheric pressure in annular space 34.

Operation of the equipment is as follows:

Hot molten metal is poured at a temperature in excess of 2000 F. In the primary mold the temperature is reduced to that necessary to set the cast metal, for carbon steel this is in a temperature range of 1200 F. to 1600" F.

In the insulating sleeve or after cooler" the temperature is reduced to a temperature in the range of approximately 300 to 600 F. and preferably to 350 to 450 F. in an atmosphere of hydrogen.

The hot metal then travels through the plating unit. In this unit, the inner chamber is the plating chamber, where the hot metal contacts an atmosphere, preferably of carbon dioxide and vapors of a volatile metal compound. These vapors may be maintained under a variety of pressures, ranging from a pressure below to pressures above atmospheric pressures and generally in the range of 6 inches of water vacuum to 6 inches of water positive pressure.

In the outer annularspace there is maintained an atmosphere of inert gas. The gas is maintained ,under a pressure generally slightly under atmospheric in order that all gas, either that inert introduced or atmospheric air leaking into this annular space 34, will be removed by the exhaust fan and there will be 'no tendency for gas to leak out, contaminating the atmosphere which must be frequented by workmen.

In the intermediate annular space 33 there is maintained an inert gas atmosphere under a pressure generally higher than is maintained in either the inner chamher or the outer annular space. While otherarrangements could be used, the high pressure is preferred for the intermediate annular space because gas fiow isjthen inward to the plating chamber through the free space around the traveling rod.

In'the plating of nickel, by way of specific example, upon a 3 inch diameter rod of cast steel, the following conditions may be maintained:

The steel maybe poured at the rate of approximately 400 pounds per minute, which rate will supply continuously cooled rod traveling at a rate of approximately 5 feet per minute.

The temperature of therod entering the plating chamber may be controlled to be approximately 425 F.

The rate of flow of gaseous medium to the plating chamber may be approximately 20 cubic feet per hour per cubic foot of chamber space, with nickel carbonyl vapors being present in the ratio ofapproximately 10 ounces of carbonyl per cubic foot of carbon dioxide gas passed through the plating chamber.

The rate of flow of carbon dioxide gas through the intermediate annular space 33 may be maintained at ap-v proximately 30 cubic feet of gas per hour per cubic foot of chamber space.

The rate of flow of gas in the outer annular ispace34 may be at the rate of 5 cubic feet perhour per cubic foot of chamber space, and the actual pressure maintained on the space by the exhaust equipment being 2 inches of water vacuum.

.It'will be understood that while the method and apparatus disclosed and described herein illustrate apreferred form of the invention, modification can'be made without departing from the spirit of the-invention, and that all modifications that fall within the scope of the appended claims are intended to be included herein."

I claim:

. 1. Apparatus for gas plating of continuous cast metal immediately upon removal of the casting from the 'mold and utilizing residual heat from the casting operation, said apparatus comprising a plating chamber arranged adjacent said mold and through which said continuously cast metal is advanced as the same is withdrawn from said mold, said plating chamber comprising an inlet and an outlet for the circulation of heat-decomposable gaseous tical passage of the casting therethrough, means for sealing the ports comprising a chamber portion surrounding each of said ports, and inlet and outlet means for circulation of inert gas to said sealing means, said chamber portion having ports aligned with the ports in the plating chamber, all of said ports providing a close sliding fit with said casting.

2. Apparatus for gas plating cast metal immediately after removal of the casting from the mold and utilizing residual heat from the casting operation, said apparatus comprising an enclosure having an inner gas lating chamber, spaced chambers surrounding said inner chamber, conduit means forming gas inlet and outlet associated with each of said chambers, means associated with said conduits for maintaining gaseous pressure difierentials between said chambers, ports in all of said chambers aligned for passage of cast metal through said chambers and providing a close sliding fit with said casting.

3. Apparatus for gas plating cast metal immediately after removal of the casting from the mold and utilizing residual heat from the casting operation, said apparatus comprising an enclosure having an inner gas plating chamber, spaced chambers surrounding said inner chamber, conduit means forming gas inlet and outlet associated with each of said chambers, means associated with the inner chamber conduits for maintaining a predetermined gas pressure, means associated With the conduit of 6 the intermediate chamber for maintaining a higher gas pressure than is maintained in the inner chamber, means associated with the conduit of the said outer chamber for maintaining gas pressure lower than the lowest in the adjacent areas, and ports in all of said chambers aligned for passage of the casting through said chambers and providing a close sliding fit with said casting.

4. Apparatus for gas plating cast metal immediately after removal of the casting from the mold and utilizing residual heat from the casting operation, said apparatus comprising an enclosure having an inner gas plating chamber, spaced chambers surrounding said inner chamber, independent conduit means forming gas inlet and outlet associated with each of said chambers, exhaust means associated with the outlet of the outer chamber for maintaining less than atmospheric pressure Within said outer chamber, and ports in all of said chambers aligned for passage of the casting through said chamber and providing a close sliding fit with said casting.

References Cited in the file of this patent UNITED STATES PATENTS 

1. APPARATUS FOR GAS PLATING OF CONTINUOUS CAST METAL IMMEDIATELY UPON REMOVAL OF THE CASTING FROM THE MOLD AND UTILIZING RESIDUAL HEAT FROM THE CASTING OPERATION, SAID APPARATUS COMPRISING A PLATING CHAMBER ARRANGED ADJACENT SAID MOLD AND THROUGH WHICH SAID CONTINUOUSLY CAST METAL IS ADVANCED AS THE SAME IS WITHDRAWN FROM SAID MOLD, SAID PLATING CHAMBER COMPRISING AN INLET AND AN OUTLET FOR THE CIRCULATION OF HEAT-DECOMPOSABLE GASEOUS METAL THERETHROUGH, PORTS IN SAID CHAMBER ALIGNED FOR VERTICAL PASSAGE OF THE CASTING THERETHROUGH, MEANS FOR SEALING THE PORTS COMPRISING A CHAMBER PORTION SURROUNDING EACH OF SAID PORTS, AND INLET AND OUTLET MEANS FOR CIRCULATION OF INERT GAS TO SAID SEALING MEANS, SAID CHAMBER PORTION HAVING PORTS ALIGNED WITH THE PORTS IN THE PLATING CHAMBER, ALL OF SAID PORTS PROVIDING A CLOSE SLIDING FIT WITH SAID CASTING. 